Mixing rotary positive displacement pump for micro dispensing

ABSTRACT

A dispensing apparatus, which is capable of delivering precise quantities of a liquid product less than one mm 3  in size, includes a drive mechanism, a housing made up of at least two input channels coupled to a chamber made up of a first portion and a second portion. First and second component liquids are delivered via the first and second input channels respectively to the chamber and the first and second input channels are disposed so that interaction is hindered between the first component liquid and the second component liquid in either input channel. At least one feed screw with a helical thread is disposed in the chamber such that when the at least one feed screw is rotated by the drive mechanism the first and second component liquids are mixed to form a liquid product and the feed screw rotation also discharges the liquid product from the chamber.

BACKGROUND OF THE INVENTION

[0001] This invention relates generally to positive displacementdispensing apparatuses for dispensing precise quantities of a liquidproduct less than one mm³ in size. More particularly, the presentinvention relates to a dispensing apparatus having a least two inputchannels enabling the dispensing of multi-component liquids utilizing afeed screw to both mix the components and dispense the liquid product.

[0002] The ability to dispense a minute, precise quantity of liquid suchas an adhesive, a conductive epoxy, a two part adhesive, or a solderpaste at precise locations on a surface is critical to a number ofmanufacturing processes, especially in the electronics industry. Theassembly of circuit boards, hard disk drives, ink-jet cartridges, andflat panel displays are just a few examples. During normal operation; itis important to both achieve and maintain high repeatability in thedispensing quantity inspite of variations in temperature, viscosity, orboth.

[0003] For some applications, the liquid dispensed is extremelysensitive to such changes, this is especially true where the dispensedliquid has a relatively high viscosity which itself varies as thetemperature changes. This can result in changes in the volume ofmaterial dispensed over time. An example of this type of problem is inthe encapsulation of integrated circuits where typically a two-partepoxy is premixed by the epoxy manufacturer and frozen. The premixedepoxy then must be shipped and then stored in this frozen state. Whenthe buyer is ready to utilize the epoxy it must first be thawed and thenused typically within a few days, and in some instances within severalhours. Thus, during normal operation the viscosity will change, both dueto temperature variation as well as the two components reacting creatingvariation in dispensed volume over time. This is true especially forthose dispensers which utilize pneumatically actuated time/pressuredispensing mechanisms.

[0004] In addition, there are also problems relating to the entrapmentof air within the liquid to be dispensed because small gas bubbles inthe liquid compress, causing sputtering and inaccuracies in the volumeof material dispensed. Another problem is the constant almost continuoususe that these dispensers can experience when operated under typicalconditions on a high volume assembly line. If the material beingdispensed hardens or degrades then the valve has to be cleaned and thiscan be a difficult operation, sometimes requiring the dispensing systemto be return to the supplier for reconditioning which results either inhigher cost requiring additional systems on hand, or else down time ofthe assembly line. The ability to rapidly and easily replace thoseportions of the dispenser which come in contact with the dispensingliquid is very advantageous.

[0005] Current dispenser technology for adhesives that are packaged astwo parts (ie. resin and hardner for two part epoxies) typically utilizestatic mixing to blend the resin and hardner together and then dispensethe mixture directly to the bondline (i.e. onto the surface desired). Astatic mixer consists of immovable blades in a short cylindrical tubethat facilitate dispersive mixing of the two parts as they exit thererespective reservoirs. This technology works well for dispense rates inthe milliliter to liter per second range typically used in theautomotive and aerospace industries in which the accuracy of dispensedvolume is not as critical due to part dimension constrains.

[0006] For dispense rates in the microliter per second range typicallyused in electronic and semiconductor manufacturing, the dispenseaccuracy is achieved using positive displacement dispenser technology.For this type of dispenser, to obtain the desired accuracies requiredone uses a single feed screw to convey the adhesive in a known volumefor each turn of the feed screw. Thus, the dispensed volume can beaccurately controlled by the feed screw motor speed. For systems thatuse a static mixer, the control typically is pneumatic pressure pushingthe adhesive through the mixer. Due to the viscoelastic behavior of mostadhesives, controlling the dispense rate and dispense end point whendispensing a bead is difficult. Static mixers can deliver flow rates inthe microliter per second range, but typically not with the sameaccuracy as a positive displacement type pump. Currently the ability toutilize positive displacement pump technology for adhesives that arepackaged as two parts, typically requires the addition of a staticmixture to blend the resin and hardner together and then feed theblended mixture through a single input channel for dispensing by thefeed screw of the positive displacement pump. Thus, there is a need toboth blend the resin and hardner together and dispense the adhesiveutilizing a single dispensing mechanism.

SUMMARY OF THE INVENTION

[0007] A dispensing apparatus, which is capable of delivering precisequantities of a liquid product less than one mm³ in size, includes adrive mechanism, a housing made up of at least two input channelscoupled to a chamber made up of a first portion and a second portion.First and second component liquids are delivered via the first andsecond input channels respectively to the chamber and the first andsecond input channels are disposed so that interaction is hinderedbetween the first component liquid and the second component liquid ineither input channel. At least one feed screw with a helical thread isdisposed in the chamber such that when the at least one feed screw isrotated by the drive mechanism the first and second component liquidsare mixed to form a liquid product and the feed screw rotation alsodischarges the liquid product from the chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1 is a block diagram of a dispensing apparatus according toan embodiment of this invention;

[0009]FIG. 2 is a cross-sectional view of a dispensing apparatusaccording to an embodiment of this invention;

[0010]FIG. 3 is a cross-sectional view of a dispensing apparatusaccording to an embodiment of this invention;

[0011]FIG. 4 is a cross-sectional view of the chamber and the inputchannels of a dispensing apparatus according to an embodiment of thisinvention;

[0012]FIG. 5 is a cross-sectional view of the chamber and the inputchannels of a dispensing apparatus according to an embodiment of thisinvention;

[0013]FIG. 6a is a cross-sectional view of the chamber according to anembodiment of this invention;

[0014]FIG. 6b is a cross-sectional view of the chamber according to anembodiment of this invention;

[0015]FIG. 7a is a cross-sectional view of the chamber according to anembodiment of this invention;

[0016]FIG. 7b is a cross-sectional view of the chamber according to anembodiment of this invention;

[0017]FIG. 8 is a perspective view of a dispensing apparatus accordingto an embodiment of this invention;

[0018]FIG. 9a is a perspective view of a dispensing apparatus showingthe disposable insert placed within the open housing according to anembodiment of this invention;

[0019]FIG. 9b is a perspective view of a dispensing apparatus showingthe disposable insert within the closed housing according to anembodiment of this invention;

[0020]FIG. 10 is a cross-sectional view of a disposable insert accordingto an embodiment of this invention;

[0021]FIG. 11 is a plan view of a dispenser tip according to anembodiment of this invention.

DETAILED DESCRIPTION

[0022]FIG. 1 schematically illustrates a viscoelastic liquid dispenserreferred to as dispensing apparatus 100. Dispensing apparatus 100 mixestwo different liquid components to form a liquid product and accuratelydispenses a predetermined amount of the viscoelastic liquid product ontosurface 27 in a manufacturing process, utilizing feed screw 50 inchamber 20 to both mix and dispense. Examples of the viscoelasticliquids which can be dispensed are an adhesive, a conductive epoxy,underfill, solder paste or other material that typically has a viscosityof the order of 10,000 to 1,000,000 Centipoise. Dispensing apparatus 100may be used to accurately dispense any one of the materials previouslymentioned as isolated structures 29 commonly referred to as dots ontosurface 27 of the order of 0.2 to 1.5 mm in diameter with a height ofthe order of 0.2 to 1.0 mm. Dispensing apparatus 100 may also be used toaccurately dispense a bead of liquid product of the order of 0.2 to 1.5mm in width and 0.2 to 1.0 mm in height at rates of the order of 0.4 to0.8 milliliters per minute.

[0023] As shown in FIG. 1 dispensing apparatus 100 typically includestwo reservoirs labeled as first reservoir 80 and second reservoir 82,each of which holds a different liquid component. First and secondreservoirs 80 and 82 are coupled to first and second delivery mechanisms70, 72 respectively. Delivery mechanisms 70, 72 preferably are syringepumps, but those skilled in the art will readily recognize that numerousother delivery mechanisms may be utilized. Diaphragm pumps, pistonpumps, or additional feed screws are a few examples of other deliverymechanisms that can also be utilized. Depending on the drive mechanismutilized, either first and second reservoirs or first and seconddelivery mechanisms are mounted to housing 40 and are coupled to firstand second input channels 30, 34 respectively. First and second inputchannels 30,34 provide liquid communication to chamber 20 and outputchannel 38 provides liquid communication to dispenser tip 39.

[0024] Feed screw 50 slidably fits in chamber 20 and is rotated by drivemechanism 60. Thus, as feed screw 50 is rotated the threads of feedscrew 50 forces both liquid components captured between the threads andthe walls of chamber 20 to compress and move in the direction of outputchannel 38 causing mixing. When the liquid product formed from themixing of the two components reaches dispenser tip 39 it is dischargedonto surface 27 forming structure 29. The accurate control of the amountof rotation of feed screw 50 provides a precise control of the rate offeed and subsequent volume of liquid product dispensed. As liquidproduct is dispensed, an additional supply of both liquid components isprovided by first and second delivery drives 74, 76 which activate firstand second delivery mechanisms 70, 72. Controller 102 controls bothdelivery drives 74, 76 and drive mechanism 60.

[0025] The incorporation of two input channels 30, 34 connected tochamber 20 provides an advantage over dispensing systems having only oneinput channel by allowing the dispensing of two-part adhesives withoutthe need for premixing, either using static mixers or frozen pre-mixedtwo part adhesives. This results in significantly lower costs, becausethe supplier can use bulk packaging compared to the custom syringestypically utilized. In addition, there is no longer a requirement forfreezing thus reducing both shipping and handling costs. Further, theunmixed two part adhesives typically have a very long shelf life at roomtemperature compared to the frozen premixed materials thus reducingscrap costs as well. Finally the utilization of two input channelsprovides the user greater flexibility in formulation chemistries thatenable low temperature curing, no filled systems, and very exothermicreacting materials which a supplier would be prohibited from shipping ina premixed frozen form.

[0026] Referring to FIG. 2, an embodiment of dispensing apparatus 100 ofthe present invention in a cross-sectional view is shown, where helicalthreads 252 extend over a substantial portion of the length of feedscrew 250 beginning near drive coupling 255 and ending near secondportion 224. Helical threads 252 have a diameter slightly less than thediameter of chamber 220, thus helical threads 252 are in sliding contactwith side wall 225 of chamber 220. In addition, in this embodiment feedscrew 250 has helical threads 252 with a relatively wide pitch nearfirst portion 222 the threads becoming narrower and closer together asthe threads approach second portion 224. Drive coupling 255 is formed atthe end of feed screw 250 located in first portion 222. Internal drivesocket 256 is formed in drive coupling 255 so that drive shaft 262 isreceived within internal drive socket 256 to provide rotational couplingbetween drive mechanism 260 and feed screw 250. In this embodiment drivemechanism 260 is preferably a servo motor or stepper motor whichprovides accurate control of the amount of rotation of feed screw 250.Drive bracket 264 mounts drive mechanism 260 to housing 240. Internaldrive socket 256 preferably is square, rectangular, or hexagonal;however, those skilled in the art will appreciate that there arenumerous other coupling mechanisms such as a screw coupling or keyedcoupling as well as others, which can be utilized. Rotary seal 254 both,maintains feed screw 250 in a centered position with respect to chamber220, and cooperates with, the opposing surface of side wall 225 ofchamber 220 to form a seal to hinder liquid components from moving intofirst portion 222.

[0027] First and second reservoirs 280, 282 in this embodiment, arerelatively large syringes, which are mounted to storage ends 232, 236respectively of input channels 230 and 234. Preferably first and secondreservoirs 280,282 are fifty to one hundred fifty milliliters in size,but may be larger or smaller depending on the particular application.First and second delivery mechanisms 270, 272 are pistons which areactivated by first and second delivery drives, which are preferably lowpressure air sources of 5-70 psi that is applied to urge viscoelasticfirst and second liquid components 104, 106 from reservoirs 280, 282into input channels 230, 234 via storage ends 232, 236. Those skilled inthe art will appreciate that if a source of low pressure air is notreadily available, then other mechanisms commonly used to move a pistoncan be utilized, as for example a screw drive.

[0028] As shown in FIG. 2 second inlet end 235 of second inlet channel234 opens into chamber 220 at a point closer to first portion 222 ofchamber 220 than first inlet end 231 of first inlet channel 230. Firstinlet end 231 and second inlet end 235 are separated in a directionalong the axis of the chamber that precludes interaction of first andsecond component liquids 104, 106 in either input channels 230, 234.Also shown in FIG. 2 is housing 240, which includes chamber 220, firstand second inlet channels 230, 235 as a unitary construction. Thoseskilled in the art will appreciate that housing 240 can be constructedfrom multiple parts fastened together that provide proper liquid sealingat points where a liquid component flows from one part to another. Notshown in FIG. 2 is controller 202 which provides signals to control bothfirst and second delivery drives 274, 276 which activate first andsecond delivery mechanisms 270, 272. Controller 202 also providessignals to control drive mechanism 260 for rotating feed screw 250.

[0029] In FIG. 2 feed screw 250 rotates within chamber 220, that hasparallel side wall 225, helical threads 252 have a variable pitch whichincreases the pressure exerted on liquid components 104,106. Analternate embodiment of the present invention is shown in across-sectional view in FIG. 3 that functions in a similar manner asthat shown in FIG. 2. In FIG. 3 feed screw 350 has a conic or taperedshape with helical threads 352 having a linear pitch. Finally, feedscrew 250, can include sections with various configurations of helicalthreads. Those skilled in the art will appreciate that kneading threads,reverse threads, variable pitch thread, cylindrical sections with nothreads all can be utilized in various combinations as well as numerousother thread designs.

[0030] When feed screw 350 is rotated helical threads 352 are in slidingcontact with side wall 325 of chamber 320. The clearance between helicalthreads 352 and side wall 325 can be adjusted. As first and secondliquid components 104, 106 are fed into chamber 320 at first and secondinlet ends 331,335 the reduction in area created by the smaller diameterof the tapered shape produces a reduction in volume leading to anincrease in pressure similar to that obtained with feed screw 250.

[0031] Referring to FIG. 4 a cross-sectional view is shown of analternate embodiment of the present invention where first and secondinput channels 430, 434 extend radially from chamber 420. First andsecond inlet channels 430, 434 are separated in a direction along theaxis of chamber 420 to preclude the interaction of first and secondcomponent liquids 104, 106 from either input channel as first and secondcomponent liquids are fed into chamber 420 from first and secondreservoirs 80,82.

[0032] Referring to FIG. 5 a cross-sectional view is shown of analternate embodiment of the present invention, where first and secondinlet channels 530, 534 are attached to chamber 520 at a commonlocation. As shown in FIG. 5 the angle formed between the axes of inputchannels 530, 534 is acute. Preferably the angle is less than ninetydegrees, however those skilled in the art will appreciate that an angleless than one hundred eighty degrees can be utilized depending on boththe feed rates and pressure differential utilized to feed first andsecond component liquids 104, 106 to chamber 520. This embodiment isvery advantageous in alleviating back flow problems for thoseapplications which require a significant feed rate differential betweenthe first and second component liquids 104, 106.

[0033] Referring to FIGS. 6a-6 b an alternate embodiment of the presentinvention is shown, where two feed screws 650′ and 650″ are locatedwithin chamber 620. FIG. 6a shows a cross-sectional view of chamber 620located in housing 640. In this embodiment, chamber 620 includes twocircular bores 610 and 612 formed in housing 640 which have parallelaxes and extend centrally and longitudinally through housing 640.Circular bores 610 and 612 communicate with each other along a commonchord 614. Feed screws 650′ and 650″ are rotatably supported withincircular bores 610 and 612 of chamber 620 and are in sliding contactwith side wall 625 as shown in FIG. 6b. Preferably the gap G betweenhelical threads 652′, 652″ and side wall 625 is of the order of 0.0001to 0.0008 inches, but may be smaller or larger depending on theparticular application, as shown in the expanded portion of FIG. 6b.Helical threads 652′ and 652″ in this embodiment are partly overlappingalong chord 614. As feed screws 650′, 650″ are rotated helical threads652′, 652″ are engaging each other in a meshing manner, as shown in FIG.6b, causing first and second component liquids 104, 106 in the turns ofhelical threads 652′ and 652″ to move in the axial direction causingmixing and the dispensing of liquid product. The intermeshing of thehelical threads 652′ and 652″ results in a volumetric transport ofmaterial. Feed screws 650′, 650″ can run in two modes: co-rotating andcounter-rotating depending on screw design where typically co-rotatingfeed screws can be operated at higher speeds.

[0034] The incorporation of two feed screws 650′, 650″ in chamber 20provides a dispenser which can dispense both, a wider range ofviscosities, especially for materials at the low end of the viscosityrange, as well as a when there is a large particle size variation. Inaddition, two feed screws provide improved mixing since the fluidicdynamics are much more complex. Thread configurations are also moreflexible utilizing two feed screws. Further, when they are intermeshing,two feed screws are typically self-wiping (i.e. self cleaning). Finally,feed screws 650′, 650″ can include sections with various configurationsof helical threads. Those skilled in the art will appreciate thatkneading threads, reverse threads, variable pitch thread, cylindricalsections with no threads all can be utilized in various combinations aswell as numerous other thread designs.

[0035] Referring to FIGS. 7a-7 b an alternate embodiment of the presentinvention is shown, where two feed screws 750′ and 750″ are locatedwithin chamber 720 that includes two non-overlapping cylindrical bores.FIG. 7a shows a cross-sectional view of chamber 720 located in housing740. In this embodiment, chamber 720 includes two circular bores 710 and712, having radius R10 and R12 respectively, formed in housing 740 whichhave parallel axes and extend centrally and longitudinally throughhousing 740. The distance D between the axis of circularbore 710 and theaxis of circular bore 712 is greater than the sum of R10 and R12.Circular bores 710 and 712 communicate with each other through commonopening 715. Feed screws 750′ and 750″ are rotatably supported withincircular bores 710 and 712 of chamber 720 as shown in FIG. 7b. Helicalthreads 752′ and 752″ in this embodiment are non-overlapping. As feedscrews 750′, 750″ are rotated helical threads 752′, 752″ cause first andsecond component liquids 104, 107 in the turns of helical threads 752′and 752″ to move in the axial direction causing mixing and thedispensing of liquid product as shown in FIG. 7b. Feed screws 750′, 750″can run in two modes: co-rotating and counter-rotating depending onscrew design. In addition, feed screws 750′, 750″ can include sectionswith various configurations of helical threads. Those skilled in the artwill appreciate that kneading threads, reverse threads, variable pitchthread, cylindrical sections with no threads all can be utilized invarious combinations as well as numerous other thread designs.

[0036] Referring to FIG. 8 an alternate embodiment of the presentinvention is shown, where housing 40 includes main body portion 840 andfront body portion 841. Front body portion 841 is attached to main bodyportion 840 at pivot point 805 through hinge 845 (not shown) so thatfront body portion 841 pivots away from main body portion 840 whenlocking mechanism 846 (not shown) is released. Main body portion 840 andfront body portion 841 cooperate to form internal cavity 890 made up ofmain cavity 891, drive cavity 892, output cavity 894, and first andsecond input cavities 896, 898. All of these cavities are formed as onehalf openings in each of main body portion 840 and front body portion841 for ease of manufacturing and assembly as shown in FIG. 8. Althoughthose skilled in the art will appreciate that these cavities need not beeach formed as one half in either main body portion 840 or front bodyportion 841. Drive shaft 862 of drive mechanism 860 is shown extendinginto drive cavity 892. Internal cavity 890 are openings for disposableinsert 818 as will be described.

[0037] Also shown in FIG. 8 is disposable insert 818 which includes feedscrew 850 and chamber 820 where chamber 820 consists of three segmentsfirst portion 822, second portion 824 and third portion 826. First andsecond inlet channels 830, 834 extend radially from third portion 826 ofchamber 820 and are separated in a direction along the axis of chamber820 to preclude the interaction of first and second component liquids104, 106 from either input channel as first and second component liquidsare fed into chamber 820 from first and second reservoirs 80,82 (notshown). Disposable insert 818 is received in housing 40 in internalcavity 890, disposable insert 818 forms a chamber complimentary tointernal cavity 890. During mixing and dispensing first and secondcomponent liquids are retained in chamber 820 and first and second inputchannels 830, 834. Therefore, during the normal course of operation theinterior walls of disposable insert 818 are the portions wetted by firstand second component liquids 104, 106 and liquid product. Thus, undernormal operation first and second component liquids 104, 106 and liquidproduct never contact any of the surfaces of internal cavity 890.

[0038] Disposable insert 818 is shown in FIG. 9a inserted into housing40 with front body portion 841 in an open position. FIG. 9b shows frontbody portion 841 with locking mechanism 846 in a locked position. Asshown in FIG. 9b locking mechanism 846 consists of captive screws 844which are threaded into threaded openings 842 shown in FIG. 9a. Thoseskilled in the art will readily recognize that there are numerous otherlocking mechanisms which can be utilized such as a latch as well asothers.

[0039] Referring to FIG. 10 an exploded cross-sectional view of disposalinsert 818 is shown where drive coupling 855 is sized to be received indrive cavity 892 (shown in FIG. 8). Feed screw shank 853 is to bereceived in chamber 820 and has a diameter slightly less than thediameter of chamber 820, thus feed screw shank 853 is in sliding contactwith side wall 825 of chamber 820. Drive coupling 855 includes drive end859, second annular shoulder 858, and first annular shoulder 857 allhaving a diameter somewhat smaller than the previous diameter going fromdrive end 859 to feed screw shank 853 (i.e. drive end 859 is of agreater diameter than second annular shoulder 858, which is of a greaterdiameter than first annular shoulder 857, which is of a greater diameterthan feed screw shank 853). When feed screw 850 is inserted into chamber820 an annular cavity is formed by face 851, first annular shoulder 857,and internal wall 821 of first portion 822 of chamber 820. Thus, face851 compresses rotary seal 854, preferably an elastomeric o-ring sealaxially, while the outer surface of first annular shoulder 857 forms aninner sealing surface, and a portion of internal wall 821 forms an outersealing surface, hindering liquid components from moving into firstportion 822 of chamber 820. Internal drive socket 856 is formed in drivecoupling 855 so that drive shaft 862 is received within internal drivesocket 856 to provide rotational coupling between drive mechanism 860and feed screw 850.

[0040] Helical threads 852 extend over a substantial portion of thelength of feed screw 850 beginning near drive coupling 855 andcontinuing to the opposite end of feed screw 850. Helical threads 852have a diameter slightly less than the diameter of chamber 820, thushelical threads 852 are in sliding contact with side wall 825 of chamber820 and helical threads 852 have a wide pitch near feed screw shank 853the threads becoming narrower and closer together as the threadsapproach second portion 824. In this embodiment drive mechanism 860 ispreferably a servo motor or stepper motor which provides accuratecontrol of the amount of rotation of feed screw 850. Internal drivesocket 856 preferably is square, rectangular, or hexagonal, however,those skilled in the art will appreciate that there are numerous othercoupling mechanisms such as a screw coupling or keyed coupling as wellas others, which can be utilized.

[0041]FIG. 10 shows second portion 824 includes outlet cap 884 whichextends beyond outlet cavity 894, output channel 838. Threads 885 areformed on the inner surface of outlet cap 884. Upper portion 886, closerto outlet cap 884, is greater in diameter than lower portion 887 forminga tapered shoulder that is used to mount a removable dispenser tip 839(shown in FIG. 11). Dispenser tip 839, shown as a plan view in FIG. 11includes blunted needle 948 of appropriate bore diameter to produce thedesired size of structure 29. Coupling unit 947 on the upper portion hasthreaded segment 949 on the outer surface and is tapered on the innersurface 943 to substantially match the tapered shoulder formed in upperand lower portions 886, 887 of second portion 824. Blunted needle 948 isattached to coupling unit 947 which is screwed into outlet cap 884 ofdisposable insert 818 for easy removal and replacement. Those skilled inthe art will readily appreciate that other mounting arrangements may beutilized.

What is claimed is:
 1. A dispensing apparatus capable of deliveringprecise quantities of a liquid product less than 1 mm in size,comprising: a drive mechanism; a housing having at least two inputchannels coupled to a chamber having a first portion and a secondportion, such that a first component liquid is delivered through a firstinput channel of the at least two input channels to the chamber, and asecond component liquid is delivered through a second input channel ofthe at least two input channels to the chamber, where the first inputchannel and the second input channel are disposed so that interaction ishindered between the first component liquid and the second componentliquid in either input channel; at least one feed screw having a helicalthread and disposed in the chamber, where the at least one feed screw,rotated by the drive mechanism mixes the first and second componentliquids to form a liquid product and discharges the liquid product fromthe chamber.
 2. The dispensing apparatus of claim 1, further comprisinga dispenser tip in liquid communication with the output channel fordispensing a controlled amount of product.
 3. The dispensing apparatusof claim 2, wherein the dispenser tip is disposable.
 4. The dispensingapparatus of claim 1, wherein the dispensing apparatus further comprisesa controller for controllably rotating the at least one feed screw. 5.The dispensing apparatus of claim 1, wherein the chamber furthercomprises a side wall, wherein the chamber is cylindrical in shapehaving an axis extending centrally and longitudinally through thehousing and the side wall forms a substantially cylindrical internalvolume.
 6. The dispensing apparatus of claim 5, wherein the first andsecond input channels extend radially from the axis of the chamber wherethe second input channel is closer to the first portion of the chamberthan the first input channel and the first and second input channels areseparated in a direction along the axis of the chamber to precludeinteraction of the first and second component liquids in either inputchannel.
 7. The dispensing apparatus of claim 1, wherein each inputchannel of the at least two input channels has an axis and are attachedto the chamber at a common location and an angle formed by the two axesof each input channel is acute.
 8. The dispensing apparatus of claim 1,wherein the two input channels further comprise an inlet end attached tothe chamber and a storage end, wherein a storage reservoir is mounted tothe storage end of each input channel.
 9. The dispensing apparatus ofclaim 8, wherein the storage reservoir further comprises a deliverymechanism to deliver liquid to each input channel.
 10. The dispensingapparatus of claim 1, wherein the chamber further comprises a thirdportion having internal walls that are substantially parallel and thechamber is cylindrical in shape where the internal walls form asubstantially cylindrical internal volume, wherein the helical threadsof the at least one feed screw are in sliding contact with the internalwalls of the third portion of the chamber.
 11. The dispensing apparatusof claim 10, wherein the at least one feed screw further compriseshelical threads having a variable pitch that decreases as the helicalthreads approach the second portion of the chamber.
 12. The dispensingapparatus of claim 1, wherein the chamber further comprises a thirdportion having internal walls that are tapered and the chamber iscylindrical in shape where the internal walls form a substantiallycylindrical internal volume, wherein the third portion has a startingdiameter near the first portion that varies becoming smaller as thewalls approach the second portion; and wherein the helical threads ofthe at least one feed screw are in sliding contact with the internalwalls of the third portion of the chamber.
 13. The dispensing apparatusof claim 12, wherein the at least one feed screw further compriseshelical threads having a linear pitch.
 14. The dispensing apparatus ofclaim 1, wherein the at least one feed screw further comprises two feedscrews having helical threads, and wherein the drive mechanism drivesthe two feed screws.
 15. The dispensing apparatus of claim 14, whereinthe chamber further comprises a third portion having two partlyoverlapping cylindrical bores and the two feed screws are rotatablysupported in the two partly overlapping cylindrical bores of the barrelbody.
 16. The dispensing apparatus of claim 15, wherein the two partlyoverlapping cylindrical bores have a region of overlap and the twopartly overlapping cylindrical bores having internal walls that aresubstantially parallel, and wherein the helical threads of the two feedscrews are in sliding contact with the internal walls of the thirdportion of the chamber and where the helical threads of the two feedscrews are inter-meshing in the region of overlap.
 17. The dispensingapparatus of claim 15, wherein the two feed screws further comprisehelical threads having a variable pitch that decreases as the helicalthreads approach the second portion of the chamber.
 18. The dispensingapparatus of claim 14, wherein the chamber further comprises a thirdportion having two non-overlapping cylindrical bores having internalwalls that are substantially parallel and the two feed screws arerotatably supported in the two non-overlapping cylindrical bores of thebarrel body, wherein the helical threads of the two feed screws are insliding contact with the internal walls of the third portion of thechamber and where the helical threads of the two feed screws arenon-intermeshing.
 19. A dispensing apparatus capable of deliveringquantities of a liquid product, comprising: a drive mechanism; at leastone feed screw having a helical thread; a housing having a main body anda front body, where the main body is attached to the front body whereinthe main body and the front body when attached form an internal cavityhaving a main cavity, a drive cavity, an output cavity and two inputcavities; a disposable insert having a chamber, a first portion, asecond portion, and two input channels where the disposable insertconformally fits within the internal cavity of the housing, such that afirst component liquid is delivered through a first input channel of theat least two input channels to the chamber, and a second componentliquid is delivered through a second input channel of the at least twoinput channels, where the first input channel and the second inputchannel are disposed so that interaction is hindered between the firstcomponent liquid and the second component liquid in either inputchannel; at least one feed screw having a helical thread and disposed inthe chamber, where the at least one feed screw, rotated by the drivemechanism mixes the first and second component liquids to form a liquidproduct and discharges a precise amount of the liquid product from thechamber.
 20. The dispensing apparatus of claim 19, wherein thedisposable insert is removable from the housing when the main body andthe front body are detached, and wherein a new disposable insertsubstantially mates with the internal cavity of the housing.
 21. Thedispensing apparatus of claim 19, wherein the housing further comprisesa locking mechanism and a hinge mechanism coupling the main body to thefront body.
 22. The dispensing apparatus of claim 19, further comprisinga disposable dispenser tip in liquid communication with the outputchannel for dispensing a controlled amount of product.
 23. Thedispensing apparatus of claim 19, wherein the two input channels extendradially from the chamber where one input channel is closer to the firstportion than the second input channel and separated by a least adistance sufficient to preclude interaction of the first and secondcomponent liquids in either input channel.
 24. The dispensing apparatusof claim 19, wherein one input channel descends to the chamber and thesecond input channel ascends to the chamber, wherein the two inputchannels are attached to the chamber at a common location and the angleformed by the two input channels is acute.
 25. The dispensing apparatusof claim 19, wherein the two input channels further comprise an inletend attached to the chamber and a storage end, wherein a storagereservoir is mounted to the storage end of each input channel.
 26. Thedispensing apparatus of claim 19, wherein the chamber further comprisesa third portion having internal walls that are tapered, wherein thethird portion has a starting diameter near the first portion thatsmoothly varies becoming smaller as the walls approach the secondportion; and wherein the helical threads of the at least one feed screware in sliding contact with the internal walls of the third portion ofthe chamber.
 27. The dispensing apparatus of claim 26, wherein the atleast one feed screw further comprises helical threads having a linearpitch.
 28. The dispensing apparatus of claim 19, wherein the at leastone feed screw further comprises two feed screws having helical threadswhere the drive mechanism drives the two feed screws.
 29. The dispensingapparatus of claim 28, wherein the chamber further comprises a thirdportion having a barrel body having two partly overlapping cylindricalbores and the two feed screws are rotatably supported in the two partlyoverlapping cylindrical bores of the barrel body.
 30. The dispensingapparatus of claim 29, wherein the two partly overlapping cylindricalbores have a region of overlap and the two partly overlappingcylindrical bores having internal walls that are substantially parallel,wherein the helical threads of the two feed screws are in slidingcontact with the internal walls of the third portion of the chamber andwhere the helical threads of the two feed screws are intermeshing in theregion of overlap.
 31. The dispensing apparatus of claim 29, wherein thetwo feed screws further comprise helical threads having a variable pitchthat decreases as the helical threads approach the second portion of thechamber.
 32. The dispensing apparatus of claim 28, wherein the chamberfurther comprises a third portion having a barrel body having twonon-overlapping cylindrical bores having internal walls that aresubstantially parallel and the two feed screws are rotatably supportedin the two non-overlapping cylindrical bores of the barrel body, whereinthe helical threads of the two feed screws are in sliding contact withthe internal walls of the third portion of the chamber and where thehelical threads of the two feed screws are non-intermeshing.
 33. Amethod of dispensing a liquid from a dispensing apparatus comprising thesteps of: introducing a first component liquid to at least one feedscrew disposed within a chamber; introducing a second component liquidto the at least one feed screw independent of the introduction of thefirst component liquid; rotating the at least one feed screw the apre-selected amount, to mix the first and second component liquidsforming a liquid product and dispense a measured amount of the liquidproduct.
 34. A method of dispensing a liquid from a dispensing apparatuscomprising the steps of: introducing a first component liquid to a firstfeed screw disposed within a chamber; introducing a second componentliquid to a second feed screw disposed within the chamber; counterrotating the first and second feed screws a pre-selected amount, to mixthe first and second component liquids forming a liquid product anddispense a measured amount of the liquid product.
 35. A method ofdispensing a liquid from a dispensing apparatus comprising the steps of:introducing a first component liquid to a first feed screw disposedwithin a chamber; introducing a second component liquid to a second feedscrew disposed within the chamber; co-rotating the first and second feedscrews a pre-selected amount, to mix the first and second componentliquids forming a liquid product and dispense a measured amount of theliquid product.